Muffler



MUFFLER 3 Shets-Sh'eet 1 W. H. POWERS INVENTOR. J va/era BY I *pil' 'Iarms/d.

March 26, 1963 Filed Oct. 28, 1960 March 26', 1963 w. H. POWERS 3,

' MUFFLER Filed 001;. 28, 1960 3 Sheets-Sheet 2 5 IN V EN TOR. M/fer 20206 715'.

Mardi 1963 w. H. POWERS 3,082,841

MUFFLER Filed Oct. 28, 1960 s Sheets-Sheet s 21%. L IE1. E

INVENTOR.

United States Patent 3,082,841 MUFFLER Walter H. Powers, Racine, Wia,assignor to Walker Manufacturing Company, a corporation of DelawareFiled Oct. 28, 1960, Ser. No. 65,767 20 Claims. (Cl. 181-S4) Myinvention relates to mufflers of the type used to silence the exhaust ofinternal combustion engines.

It is the object of my invention to greatly reduce o eliminate thecorrosion of exhaust muffiers.

In accomplishing the object of my invention I coat the surfaces of themufiler with an anti-corrosive ceramic material of a type available onthe open market and which can be applied to a steel surface. I havefound that it is best to coat the muffler surfaces after assembly ratherthan to try to coat the surfaces of individual parts or subassemblies.Thus, I contemplate the dip coating of the muffler in an anti-corrosiveceramic slip. My invention provides a muffler construction that can besuccessfully coated with ceramic by the dipping process or by otherprocesses if desired.

The conventional muffler contains a series of internal chambers withinan outer shell. These form many internal pockets that interfere with theproper drainage of liquids and gases during the coating process.Improper drainage at various stages of the ceramic coating process isvery likely to result in incomplete surface coverage and probably insubsequent rust-out at the uncovered areas.

Thus, a further object of my invention is to provide a mufflerconstruction with means for external and internal drainage so that itcan be properly ceramic coated.

The invention provides for proper drainage by means of holes located atthe correct positions in the various internal chambers. These arelocated and sized so that they do not have an adverse acoustic effect.The term drainage opening or drainage hole as used hereinafter refers toopenings or holes whose primary purpose is for drainage or ventingduring the coating of a muffler, as distinct from holes intendedprimarily for exhaust gas flow or for acoustic purposes.

My invention is illustrated in the accompanying drawings in which:

FIGURE 1 is a side elevation, somewhat diagrammatic, showing the muffler1 in position for dipping in a bath of suitable corrosion resistingceramic;

FIG. 2 is a longitudinal cross-section through a typical mufiler thatmay be dip coated in accordance with the principles of this invention;

FIG. 3 is an end elevation taken from the left of FIG. 2;

FIG. 4 is an end elevation taken from the right of FIG. 2;

FIG. 5 is a cross-section taken along the line 5-5 of FIG. 2;

FIG. 5A is a cross-section showing a modified form of partition that iscut off to provide air and liquid escape holes;

FIG. 6 is a cross-section taken through the plug of FIGS. 3 and 4;

FIG. 7 is a cross-section through the plug of FIG. 6 prior to insertion;

FIG. 8 is a section similar to that of FIG. 6 showing a modified form ofplug;

FIG. 9 is a view taken from the right of FIG. 8;

FIG. 10 is a section similar to that of FIG. 8 with still another formof plug;

,FIG. 11 is a view similar to that of FIG. 9 taken from the right ofFIG. 10;

. FIG. 12 is a side elevation of the plug of FIGS. 10 and 11; and

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FIG. 13 is a side elevation of the plugs of FIGS. 10-12.

FIG. 1 illustrates dip ceramic coating of a carbon steel muffler 1A. Theceramic is in the form of a suitable slip or bath 3 contained in asuitable tank 5. The muffier 1 may be suspended by a book 7 whichprovides the means for lowering the muffler down into the bath and afterall surfaces, internal and external, have been coated, for removing themulller from the bath 3.

FIG. 2 is a longitudinal cross-section through a typical mufller 1. Itdiffers slightly from the muffler 1A illustrated in FIG. 1 in that itshows a layer of asbestos 9 wrapped around the muffler casing 11 andheld in place by an external layer of sheet metal 13. In the coatingprocess I prefer to omit the asbestos layer 9 and the sheet metal 13since the asbestos 9 will tend to soak' up the various liquids involvedand the material so absorbed may create difliculties in the subsequentcoating and firing of the ceramic dipped muflier.

The muffler 1 has a casing 11 which is formed of sheet steel (as are theinternal parts) that is rolled into an oval shape and the overlappingedges spot-welded together or lock-seamed in accordance with standardpractice. In the form shown in FIG. 2, the lock-seams would be along thebottom edge of the shell 11. The opposite ends of the casing 11 areclosed by the headers 15 and 17. The outer peripheries of the headersare tightly connected to the end of the casing 11 in interlocked joints19 and 20 and in accordance with the invention the top sides of thejoints 19 and 20 (opposite the shell joint) are bent inwardly ordownwardly so that the outer surface of the casing 11 is exposed at eachend, thus enabling the outer shell 13 to be formed as a sheet andwrapped around the layer of asbestos 9 and then lock-seamed bylock-seaming equipment which passes over the flat bentin portions 20'after the muffler 1A has been coated and fired.

The silencing structure Within the mufiier shell 11 is typical ofvarious types that can be used and will illustrate how such structureshould be adapted for the application of protective coatings presentingthe same problems as a dip ceramic coating. Thus, the interior of thecasing 11 is divided into a series of longitudinally separated chambers21, 23, 25, 27, and 29 by a series of transverse sheet steel partitions31, 33, 35, and 37. Each of the transverse partitions has, in accordancewith the usual practice, an annular flange around its outer peripheryand this is spot-welded to the casing 11. Gas enters the casing 11through an inlet bushing 39 which is supported in and spot-welded to aneck 41 formed in the inlet header 15. The inner end of the bushing 39is necked-down or reduced in diameter at 44 and is supported in andspot-welded to a neck 45 in the partition 3-1. The extreme inner end ofthe bushing 39 has a slit or slotted flare 47 to facilitate theinsertion of the end of an inlet conduit 49, such conduit being slippedinside of the reduced end 44 of bushing 39 at assembly when it and theassociated parts to be described are inserted inside of the shell 11.The conduit 49 is supported in and spot-welded to flanged necks 51 and53 of the partitions 33 and 35, respectively. A pair of sets of louvers55 within the walls of the conduit 49 permit sound waves to enter spitchambers 57 that are formed around the conduit by means of apancake-type chamber-forming construction 59 consisting of complementalstamped halves that have flanges that are spotwelded together and neckswhich are spot-welded to the conduit 49, such construction being morefully described in my copending application, Serial No. 575,404, filed 1April 2, 1956.

Gases leaving the inlet conduit 49 enter the chamber 27 and reverse thedirection of flow to go back toward the inlet end of the muliler. Indoing this, the gases flow back through the volume of the chamber 25between the partitions 33 and 35. These partitions have a series ofrelatively large openings 61 formed in them so that the gases can flowfreely and without restriction from the chamber 27 to the chamber 23.Gases in the chamber 23 flow toward the outlet header 17 through anoutlet conduit 63 which is supported in and spot-welded to necks 65 and67 formed respectively in the partitions 33 and 35. The section of thetube 63 within chamber 25 may be provided with louvers 69 opening intothe chamber 25. The outer end of .the outlet tube 63 is slidably fittedin and supported in the inner reduced end 71 of the outlet bushing 73which is expanded and spot-welded to the neck 7-5 in the outlet header17. The inner end 71 of the bushing 73 is slit and flared slightly at 77to enable it to be slipped over the end of the tube 63 and is alsospot-welded to the neck 79 in the partition 37. The slits in flares 77and 47 facilitate ceramic drainage as will be self-evident hereinafter.

An unusually long tuning tube 81 is supported in and spot-welded toflanged necks 83, 85, and 87 of the partitions 31, 33, and 35, beingspot-welded to the latter two partitions only. The tube 81 isimperforate and connects the crossover chamber 27 to the chamber 21 andsince it provides the only inlet and outlet to such chamber it isapparent that this constitutes a resonator chamber for notes of lowfrequency. The chamber 29 at the outlet end of the muifler is arrangedto act as a resonator chamber by means of a relatively short tuning tube91 which is spot-welded in a flanged neck 93 of the partition 37 and oneend thereof is preferably spot-welded to the bushing 73.

Coating an assemble-d muffler, such as the one just described, with aceramic material involves a series of processing steps or operationssuch as the following. First, the mother is heated to about 1300" F. andheld for 5. minutes or so to burn off grease, soap, oil, etc. Aftercooling, the muflier is detergent washed by dipping for about -20minutes in either or both alkali and acid baths, depending upon thematerials to be removed, and water rinsed after each wash. Next it 'isheld in a pickling bath, or acid bath, to roughen the surface so as topromote a 'bond with the ceramic. After this, it is rinsed and dipped ina neutralizing bath and rinsed again. Next it is dipped in a nickel bathto give it a primer coating that promotes the bond with the ceramic.Then it is rinsed and neutralized if necessary. After any or all of thevarious liquid dipping operations of the type just described have beencompleted (the order may be varied), the muffler may be held in a tankin which hot dry air is blowing so that it can be dried out.

After the foregoing or equivalent preparatory step are completed and themuffler surfaces are clean and prepared for ceramic, the muffler isdipped in a bath 3 of anticorrosive ceramic slip, drained, dried in hotair, and fired in a furnace at about 1500 F.

It will be recognized that the success of most of the above steps isdependent upon the admission of a fluid to the interior of the mufilerso that it contacts all of the muifler surface and then the drainage ofall of such fluid from the the interior of the muffler so that the next,

fluid can contact all of the muffler surfaces. In the steps involvingliquids (such as detergent'washes, rinses, pickling, neutralizing, andnickel coating) the muflier is preferably suspended from one end,lowered into a bath containing the liquid, raised out of the bath, anddrained by gravity flow "of the liquid out of the mufller and back intothe bath. In mass production of ceramic coated automobile mufflers it isnot only necessary that these various operations be performed well butthey must also be performed quickly and automatically without the needfor individual attention and inspection. The effectivenes with which thesurfaces are contacted by the various fluid and the completeness ofsubsequent drainage as well as the speed with which the fluid enter andleave the mufller all depend upon the use of the proper suspension meansand drainage means in the muffler itself. The drainage means, however,must not adversely affect the acoustic characteristics of the muffler.

Referring first to the suspension means, this comprises holes 161 and103, respectively, in the inlet and outlet bushings 39 and 73. Theseholes receive the end of a hook 7 or other suitable suspending device. Avertical line from the hole 101 or 103 through the center of gravity ofthe rnufller when suspended determines the angle of inclination of themufller, especially the angle the various transverse partitions,headers, and walls will make to the horizontal. It is evident that in nocase can the mother be suspended by holes 191 and 103 so that thetransverse walls will be perfectly horizontal. Thus, whether the muffleris suspended from the inlet or the outlet end, each chamber will have alow point toward which liquid in the chamber will flow. In the case ofthe fiat interior partitions 31, 33, 35, and 37 these low points will beat the corners between the small diameter ends of the partitions and theshell. At these corners I provide internal drainage means in the form ofsmall openings 111 and 113, respectively, which are preferably aboutinch in diameter and as close as possible to the shell wall.Alternatively, the ends of'the partitions could be sliced off as shownat 114 in FIG. 5A to provide drainage openings. It wiil be noted thatwhen an opening 111 is on the low side the corresponding opening 113will be on the high side of the adjacent chamber. Thus, as liquidescapes, air can enter to prevent a vacuum lock in the mother duringdrainage.

The end headers 15 and 17 of the mufller are provided with externaldrainage means in the form of large (preferably 1 inch diameter)openings 1614 and 105, respectively, each of which has an outwardlyextending neck 107. These openings are closed after the coatingoperation is completed by flanged, cup-shaped caps 108 as will bedescribed hereinafter. Additionally, end header 15 may be provided witha inch drain hole 106 and header 17 with three such drain holes locatedas shown in FIGS. 3 and 4. More of these holes may be used if desiredsince they are small enough to plug up with ceramic during the coatingoperation and therefore do not cause adverse acoustic effects.

The spit chambers 57 are provided with internal drainage means in theform of holes 117 and 119 located in diagonally opposite corners, theholes 117 being on the inlet and plug 194 sides of the chambers. Theholes 117 are preferably about A inch in diameter and as close aspossible to the end walls of the chambers 57 so as to eliminate anypockets that might retain liquid during draining.

The coating operation is carried out with the mutfler just described,that is, the muffler of FIG. 2 but before the plugs 108 have beeninserted or the outer layers 9 and 13 added to the shell 11. During thepreparatory steps, wherein the muffler is dipped in various free flowingliquids as outlined above, the mufiier is preferably suspended from thesuspension hole 161 in the inlet bushing 39. The muffler will hang at anangle defined by a line through the hole 101 and the center of gravity.When this is done the holes 104 and 165, respectively, will be veryclose to, if not actually, the high and low points of the space insidethe shell 11. When the muffler is suspended from the bushing 39 andlowered into a liquid bath, the liquid will enter hole and bushing 73and flow upwardly toward the inlet header 15. The air replaced by thisliquid can escape externally through openings 104 and 106 in the header15 as well as through inlet tube 49 and bushing 39. Air in the internalchambers can escape through the uppermost of the various internaldrainage openings, in this case, the openings 111 and 117. Liquid canenter the internal chambers through the various tubes as well as throughthe lower openings 113. After the muffler is completely submerged andheld for the desired period of time it Will be raised out of the bathand suspended over it so that the liquid will drain-outprincipall-ythrough opening 105. Internally the liquid will drain from one chamberto the next through the lower opening 111 and air can enter from the topto replace it through the same openings as it flowed through to leavethe muffler. Liquid in spit chambers 57 will drain into tube 49 throughlow openings 119. The centrally located hole 106 in header 17 Willprovide an outlet for any liquid tending to form a puddle in the concaveportion of the header. The foregoing arrangement of suspending means anddrainage means will enable free flowing liquid to enter and completelyleave the mufller without any shaking or agitation, thus facilitatingmass dipping of the mufflers without individual attention by anoperator.

The ceramic slip 3 is considerably thicker and more viscous than theliquids used in the various preparatory steps and thus flows more slowlythan the other liquids. In order to decrease the time required to coatthe muffler 1 with ceramic slip, I prefer to suspend it from the outletbushing hole 103 so that it is oriented more or less as shown in FIG. 1.When this is done the chamber 21 instead of the smaller chamber 29 willbe on the bottom. Thus, slip can enter and leave the chamber throughlarge opening 104 instead of openings 111 and 113 and the time requiredto fill and drain the muffler with slip is reduced substantially. Afterdipping in the bath of slip 3, a hook (not shown) is used to engage head20 and pivot the muffler up about 45 to the left in FIG. 1, thus puttingthe various drainage holes at the loW points in their respectivechambers. After dipping in slip 3, the mufflers are shaken somewhat bythe operators so that the slip is agitated sufliciently to drain out.This contrasts with the drainage during the preliminary steps which isaccomplished without shaking of the muffler.

After the muifler has been lifted from tank 3 and drained over it, it isdried to remove as many fluids as possible before firing. The drying mayinclude a step of subjecting the muffler to circulating hot air (as isdone after the preparatory steps) and it will be noted that the locationof hole 104 on a side opposite tube 81 will pre-' vent short-circuitingsuch as might occur if the hole were located on the other side of header15. During firing of thernutfler at an appropriate temperature, normallyabout 1500" F., it is preferably suspended by hole 101 as this will tendto minimize distortion that might occur due to the heat.

After firing the ceramic is cleaned off the butt ends of necks 107 toexpose metal and plugs 108 are inserted in holes 104 and 105. The plugsare hat-shaped and preferably formed of a non-corrosive, high chromemuffler steel. The flanges 109 on the plugs have projections or ribsformed on them to engage the cleaned edges of necks 107. Both plugs areprojection-welded to the necks in one cycle by simultaneous engagementof both plugs with welding electrodes, the welding current flowing fromthe plug at one end of the muflier through the mufiier shell, which actsas a conductor, to ground or the low potential side by way of the plugat the opposite end of the shell. After this the interiors of the plugsare expanded radially as seen at 110 to engage behind the headermaterial surrounding the holes 104 and 105 and provide a positiveengagement-against blow-out. v The ceramic layer will build up on theedges of and tend to bridge the various holes and reduce them in size.In order to obtain the desired results, I prefer to make the variouslouvers, such as louvers '55 and 69, of rectangular shape and about030-040" oversize to avoid clogging or bridging.

In FIGS. 8-13 I have illustrated a different method of plugging theopening in the header. In this form the opening 150, as shown in FIG.11, is not flanged and would be preferably about 1 inch in diameterandarcs 151 extending through approximately a quarter-circle would'beslit in the material surrounding the opening to form partly annular tabswhich would be slit diametrically along line 153 and then lifted up fromthe plane of the header 155 as seen in FIG. 10. The plug 157 Willcomprise a flat plate having a rectangular dished T portion 159 whichwill receive some type of instrument, such as a screw driver, so thatthe plug can be twisted into place. Sections of the periphery of theplug are slit and deformed from the plane of the plug surface in amanner complementary to the ears 151 so that, as seen in FIGS. 89, theplug can be inserted in the openings and then twisted so that thesesections will lie over and under the ears 151 and the plug willinterlock with the header 155. The plug is coated with ceramic beforeinsertion so that upon firing a gas-tight seal is obtained.

While, as illustrated, the principles of my invention are shown inconnection with ceramic coating, it is possible for these features to beused in the coating of'muiflers or other sheet metal devices by othermeans, such as painting or gaseous diffusion, wherever ventilation ofthe interior of the muflier may be required during the process.

I claim:

1. A rnuflier for dip coating and draining comprising an elongatedcasing having end Walls at opposite ends, Wall means inside said casingforming a plurality of chambers in the casing, said Wall means having atleast two spaced small drainage openings located adjacent the casingtherein with at least one pair for each chamber, the openings of eachpair being located so that they are vertically spaced from each otherwhen the mufiler is dipped in a ceramic bath or the like, one of theopenings in each pair comprising an air inlet and outlet for its chamberand being located at an uppermost portion of the chamber when themuffler is dipped so that the internal surfaces of the muffler arecoated by elimination of air pockets within the muffler.

2. The invention set forth in claim 1 wherein said end walls each havean opening therein and plugs fitting in said opening and secured to saidwalls to close the openings, said end wall openings providing externaldrainage means for the flow of air and liquid into and out of themuffler during dipping.

3. A muffler comprising a housing having end headers and internalsilencing structure, at least two spaced small internal drainageopenings provided in said silencing structure adjacent said housing,said end headers having relatively large external drainage openingstherein whereby the internal surfaces of the mufiier may be coated byflow of a coating material through the muffler during a coatingoperation, and plugs inserted in said external drainage openings toeliminate adverse effects of said external drainage openings uponoperation of the muffler, said plugs having sections overlapping theinside of the headers whereby pressure within the mufller will force thesections against the headers to prevent blow-out of said plugs duringuse of the muffler.

4. A muffier comprising a shell having end headers at opposite ends andsilencing structure including transverse partitions inside, at least twospaced small internal drainage openings provided in said silencingstructure adjacent said shell, one of said headers having a largeexternal drainage hole therein, the other end of said shell having asuspension means formed thereon, said external drainage hole andsuspension means being located so that an imaginary line betweenthempasses in close proximity to the center of gravity of the rnuflier,said drainage openings and hole providing for drainage and venting ofthe muifler interior during a dip coating operation.

5. The invention set forth in claim 4 wherein said imaginary line isnon-perpendicular to said transverse partitions, and at least two ofsaid internal drainage openings being in each of said partitions onopposite sides thereof adjacent the shell.

6. A mufiier comprising a sheet steel outer shell, internal silencingstructure in the shell, said shell being coated with ceramic, at leasttwo spaced small drainage openings in said internal silencing structureadjacent said outer shell to 7 provide for flow of coating liquidtherethrough and a layer of asbestos around the outside of said shell incontact with the coating of ceramic, and protective wrapper meansholding the asbestos in place to protect the ceramic coating on saidshell.

7. A muffler of the type having an elongated casing closed by headermeans and having internal conduits and partition means dividing thecasing into a plurality of chambers, said partition means having atleast two spaced small drainage Openings located adjacent the casing,and said Openings being arranged to enable ceramic slip or the like whenapplied internally to coat all interior parts of the muffler.

8. The invention as defined in claim 7 and wherein the spaced smallopenings of adjacent partition means are arranged to be located ondifferent horizontal levels when ceramic slip is applied to the mufllerto provide for escape of air and entry of slip between chambers.

9. The invention as defined in claim 7 and wherein said header meanshave relatively large drainage openings provided therein, and plug meansmounted in said relatively large drainage openings with sectionsoverlapping the inside of the headers whereby pressures created withinthe muffler during use will force the sections against the headers andretain the plug means in place in the drainage openings.

10. The invention as defined in claim 7 and wherein one of said headermeans is provided with a relatively large drainage hole therein at oneend of said mutller, and the other of said header means on the other endof said mufiler having suspension means integrally formed thereon tosupport said muffler during internal application of ceramic slip or thelike, said relatively large drainage hole and said suspension meansbeing located on said header means so that an imaginary line extendingbetween them passes in close proximity to the center of gravity of themufller.

11. A mufiler of the type having an elongated substantially oval casingclosed by header means and having internal conduits and oval partitionmeans dividing the casing into a plurality of chambers, the casinghaving top and bottom wall portions connected by side wall portions,said partition means having at least two oppositely arranged smallinternal drainage openings adjacent the wall portions of the casing,said openings providing liquid drainage and air vent paths within themuffler between each of said chambers.

2. An internally coated mutiier of the type having an elongated casingclosed by header means and having internal conduits and partition means,said partition means having at least two oppositely arranged smallinternal drainage openings adjacent the casing, said openings enabling acoating material or the like when applied inernally to coat all internalparts of said muiilerI 13. A mufiler having an internal ceramic coatingsubstantially completely covering the internal surfaces thereof and ofthe type having an elongated closed casing and having internal conduitsand partition means, said partition means having at least two oppositelyarranged small internal drainage openings adjacent the casing, saidcasing having external drainage openings at the ends thereof; saiddrainage openings enabling ceramic slip or the like when appliedinternally to coat all internal parts of said muffler.

14. A muil'ler having an internal ceramic coating substantiallycompletely covering the internal surfaces thereof and of the type havingan elongated substantially oval casing closed by header means and havinginternal conduits and oval partitions dividing the casing into aplurality of chambers, said oval partitions having major and minor axes,the casing having top and bottom wall portions locatedadjacent the endsof the minor axes of said partitions and side wall portions locatedadjacent the ends of the major axes of said partitions, said ovalpartitions having at least two oppositely arranged small internaldrainage openings adjacent the side wall portions of the aosasar casing,said openings enabling ceramic slip or the like when applied internallyto coat all the internal parts of the mufiier.

15. A mufller adapted to be coated after assembly of internal parts bydipping in a ceramic bath comprising an elongated casing, said casinghaving header means closing opposite ends, transverse partition meansdividing the casing into a plurality of chambers, hanger receiving meansprovided on at least one end of said casing and located to support saidmufiler during a coating operation in a tilted position with thelongitudinal axis of the muffler inclined to the vertical, and saidpartition means having at least two small spaced internal drainageopenings located closely adjacent the casing and spaced from one anotherand the center of gravity of the mufller so that one of said two smallopenings acquires a position vertically spaced from the other of saidsmall openings when the muffler is supported by said hanger receivingmeans to provide for drainage and venting of said chambers internally ofsaid muffler during a coating operation.

16. A mufiler adapted to be coated after assembly of internal parts bydipping in a ceramic bath comprising an elongated casing, said casinghaving header means closing opposite ends, transverse partition meansdividing the casing into a plurality of chambers, hanger receiving meansprovided on at least one end of said casing and located to support saidmuffler during a coating operation in a tilted position with thelongitudinal axis of the mufller inclined to the vertical, saidpartition means having at least two small spaced internal drainageopenings located closely adjacent the casing and spaced from one anotherand the center of gravity of the mother so that one of said two smallopenings acquires a position vertically spaced from the other of saidsmall openings when the mufiler is supported by said hanger receivingmeans to provide for drainage and venting of said chambers internally ofsaid mufiler during a coating operation, external drainage holes formedat the ends of the casing to provide for drainage and vent ing of thecasing as a whole during dipping in a ceramic bath, and closure meansfor covering said external drainage holes after coating.

17. A mufller adapted to be coated by being suspended in a ceramic bathcomprising an elongated casing, headers closing the ends of the casingand having inlet and outlet bushings, a plurality of transversepartitions forming chambers inside said casing, said partitionsextending at right angles to the longitudinal axis of the mufiler, oneof said bushings having a hook receiving hole therein, said hole beinglocated so that an imaginary line through it and the center of gravityof the muffler will be inclined to the longitudinal axis of the mufllerwhereby said partitions will be at an angle to the horizontal when themuffler is suspended by said hook hole, and at least twosmall spacedinternal drainage openings provided in said partitions adjacent thecasing for drainage and venting of said chambers when said mother issuspended in a bath by means of said hook hole.

18. A muffler adapted to be ceramic coated after assembly by dipping,comprising an elongated casing, headers closing opposite ends of thecasing and having inlet and outlet bushings therein, transversepartitions dividing the easing into a plurality of chambers, a supportopening for a hook provided in one of said bushings to enable saidmuffler to be suspended during dipping in a bath, at least two smallspaced internal drainage openings provided in each of said partitions onopposite sides thereof and adjacent the casing, said internal drainageopenings providing for internal venting and draining of said chambersduring dipping of the assembly muffler in a bath, the header at the endopposite to said hook support opening having a relatively large externaldrainage opening therein to provide for external draining and venting ofthe mufll'cr during dipping in a bath, said external drainage openingand said hook opening being located so that an imaginary line extendingtherethrough is located close to the center of gravity of the mufflerand inclined to the longitudinal axis of the muflier whereby saidexternal drainage opening will be substantially at the low point of themuffier and said partitions will be inclined to the horizontal when saidmuffler is suspended by means of said hook support opening, said twointernal drainage openings in each partition being located so as to berespectively at substantially the high and low points of theirrespective partitions when said rnufiier is suspended by means of saidhook support opening, the head-er at the hook support opening end ofsaid mufller being provided with a relatively large external drainageopening.

19. A rnufller for dip-type ceramic coating or the like, comprising anelongated casing having a longitudinal axis, transverse partitionsinside the casing extending at right angles to said axis, suspensionmeans on the rnufller for vertically suspending said muffier so thatsaid longitudinal axis is inclined to the vertical and said partitionsare inclined to the horizontal whereby coating liquids in said chamberstends to accumulate in a lowermost portion thereof when the mufiler issuspended by said suspension means, said partitions having at least twospaced openings formed therein located adjacent the casing, one of saidopenings being located in the lowermost portion to provide for drainageof liquid from said lowermost portion and the other of said openingsbeing located above said one opening to provide for venting of saidchambers when said muffler is suspended by said suspension means.

20. The method of manufacturing a mufller having an elongated casingclosed by header means and internal gas passages and partition meansdividing the easing into a plurality of chambers, comprising the stepsof; forming drain passage means, including at least two spaced smalldrainage openings adjacent said casing in said mufiler; assembling themuflier; and thereafter dipping the assembled muffler in a ceramic slipor the like to internally coat the mufiler.

References Cited in the file of this patent UNITED STATES PATENTS2,186,062 Berg et al. Jan. 9, 1940' 2,391,468 Long Dec. 25, 19452,395,005 Kuhn Feb. 19, 1946 2,598,756 Brightly June 3, 1952 2,618,354Hedrich Nov. 18, 1952 2,798,569 Fischer I July 9, 1957 2,825,421 BryantMar. 4, 1958 2,853,148 Billey Sept. 23, 1958 2,922,485 Muller Jan. 26,1960 FOREIGN PATENTS Australia Feb. 10, 1948

1. A MUFFLER FOR DIP COATING AND DRAINING COMPRISING AN ELONGATED CASINGHAVING END WALLS AT OPPOSITE ENDS, WALL MEANS INSIDE SAID CASING FORMINGA PLURALITY OF CHAMBERS IN THE CASING, SAID WALL MEANS HAVING AT LEASTTWO SPACED SMALL DRAINAGE OPENINGS LOCATED ADJACENT THE CASING THEREINWITH AT LEAST ONE PAIR FOR EACH CHAMBER, THE OPENINGS OF EACH PAIR BEINGLOCATED SO THAT THEY ARE VERTICALLY SPACED FROM EACH OTHER WHEN THEMUFFLER IS DIPPED IN A CERAMIC BATH OR THE LIKE, ONE OF THE OPENINGS INEACH PAIR COMPRISING AN AIR INLET AND OUTLET FOR ITS CHAMBER AND BEINGLOCATED AT AN UPPERMOST PORTION OF THE CHAMBER WHEN THE MUFFLER ISDIPPED SO THAT THE INTERNAL SURFACES OF THE MUFFLER ARE COATED BYELIMINATION OF AIR POCKETS WITHIN THE MUFFLER.